Son of Heaven and Heavenly Qaghan: Sui-Tang China and its Neighbors by Pan Yihong: The conquest of the last of the Southern Dynasties by Sui in 589 brought to an end the Period of Disunion which had started with the collapse of Han in 220 C.E. The Sui dynasty was short-lived but laid the foundation for the Tang (618-907), an age of outstanding political and cultural achievement to which later generations looked back with nostalgia....